The invention relates to a method for determining the concentration c of an absorbent homogeneously distributed in a carrier, in which the absorption a(.lambda.) of the absorbent is measured while the value of spectral absorption .epsilon.(.lambda.) is known, using Lambert-Beer's law a(.lambda.)=.epsilon.(.lambda.).c.d as a basis.
In a variety of applications it is necessary to determine the concentration c of a substance by means of an absorption measurement. Departing from Lambert-Beer's law EQU a(.lambda.)=.epsilon.(.lambda.).c.d
the concentration c is computed from the absorption measurement a(.lambda.), the spectral absorption curve .epsilon.(.lambda.) and the film thickness d being known.
On the other hand it is often necessary in such applications that the film thickness d be calibrated or at least checked at regular intervals, as any error would have its direct effects on the computed value calculated of the concentration c. Such calibrations or checks are usually performed with the use of a medium whose concentration and spectral absorption behavior are fully known.
Series production of such a calibrating medium therefore requires extreme precision in the fabrication process, which cannot always be achieved at a reasonable cost. Instead, every batch is carefully measured before leaving the production plant, and the target values obtained are noted on an enclosed data sheet. In this instance the responsibility for adequate calibration of the equipment rests with the user. The disadvantage of this method is that a number of new sources of error are introduced, such as enclosing a wrong data sheet in the instance of different batches, reading errors, wrong input data, etc.